The present invention relates generally to packaging systems that deform a web of flexible material into product-holding cavities and, more particularly, to a lift mechanism that raises and lowers a tool such as a formation box incorporated in the packaging system.
Conventional packaging systems that deform a web of flexible material into product-holding cavities, such as described in U.S. Pat. No. 4,915,283, have a forming tool that is indexed between a raised and a lowered position by a motor and cam-type arrangement in which structure defining a series of cam slots is mounted to the forming tool, and actuating arms are mounted to and rotatable with a pair of rotatable members that are driven through a timing belt or the like in response to rotation of the motor output shaft. A cam follower, in the form of a roller member, is mounted to each arm and is engaged within the cam slot, and alternating clockwise/and counterclockwise rotation of the rotatable members cause back and forth movement of the rollers within the cam slots to lift and lower the forming tool in an indexing fashion. One of the drawbacks of such conventional designs is the eccentricities involved in translating rotational movement of the lift arm into vertical movement of the forming tool, which requires relatively close tolerances in manufacture and results in uneven wear between the rollers and the surfaces of the cam slots.
Therefore, one object of the present invention is to provide a lift mechanism for raising and lowering a tool, such as a formation box or the like, which eliminates the eccentricities of cam-type designs and which is capable of being precisely controlled. In this regard, in accordance with one aspect of the invention, a lift mechanism operatively associated with a tool of a packaging apparatus that acts on web material includes a pair of arms coupled to the tool, which are moveable between a first position and a second position. More particularly, the pair of arms raises the tool when moved from the first position to the second position. The lift mechanism further includes a slave drive coupled to the pair of arms and adapted to translate between a third position and a fourth position. The slave drive moves the pair of arms from the first position to the second position so as to raise the forming box when translated from the third position to the fourth position, and moves the pair of arms from the second position to the first position so as to lower the forming box when translated from the fourth position to the third position. A master drive is coupled to the slave drive and is adapted to translate the slave drive between the third and fourth positions.
According to another aspect, the invention is directed to a tool apparatus for a packaging assembly that acts on a sheet of web material, such as by forming the web material to define a series of cavities for receiving products to be packaged. The tool apparatus includes a lift mechanism operatively associated with a tool for moving the tool between a lowered position and a raised position. The lift mechanism includes a pair of arms associated with the tool, and a slave roller to which the pair of arms are associated. The slave roller is moveable between a first position and a second position along a linear path that is perpendicular to the path of movement of the tool. The slave roller positions the tool at the lowered position when moved to the first position, and positions the tool at the raised position when moved to the second position. The lift mechanism further includes a master roller associated with the slave roller and operative to move the slave roller along the linear path between the first position and the second position.
According to another aspect of the invention, a packaging apparatus includes a web supply containing a sheet of web material and a web advancement assembly associated with the web supply. The packaging apparatus further includes a cavity formation assembly adapted to form cavities in the sheet of web material. The cavity formation assembly includes a formation box that is reciprocated between a lowered position and a raised position by movement of a pair of arms in a cooperative spaced arrangement, wherein movement of the arms towards one another raises the formation box and movement of the arms away from one another lowers the formation box.
Other aspects, features, and advantages of the invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.